A sustainable and low-cost route to design FeNi alloy/carbon-decorated coal fly ash with enhanced microwave absorption

The recycle of coal fly ash (CFA) is of momentous value to relieve the growing levels of the serious environment pollution. Herein, light-weight and low-cost microwave absorption (MA) materials CFA based composites assisted by carbon and FeNi alloy (FeNi/C-CFA) were constructed by an impregnation-carbonization process. The actions of the loading of carbon network and Fe/Ni species distributed in the CFA matrix, and the MA performances of FeNi/C-CFA composites were assessed in detail. The results showed that the FeNi/C-CFA with wrapping structure exhibited the minimum reflection loss (RLmin) of -39.2 dB with the coating thickness of 3.5 mm, while the effective absorption bandwidth (EAB) was measured to be 4.8 GHz (10.6–15.4 GHz) at a coating thickness of 2.0 mm. Their favorable MA performances were mainly from combined actions of the unique morphologies, good impedance matching and improving attenuation characteristics. Thus, these MA materials recycling from solid waste CFA may be a potential candidate for eliminating electromagnetic pollution along with the source abundance, low-cost, lightweight and easy preparation.